XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2933
Tailings sample. As mentioned earlier, for comparative
purposes, an arbitrary retention time of 14 minutes was
chosen for the bench flotation reference, assuming a tail-
ings retreatment plant (TRP) with a capacity of around 36
minutes.
As was the case for the Cleaner feed, interpretation of
the results should be done against the seeming fact that the
assay of the final concentrate in the baseline test (0 pass)
was erroneously over-reported, coupled with an excessive
mass pull. This is also evident from the shape of the other
three curves, as would be expected from a typical bench
float. Likewise, the assay of the first concentrate after 5
passes seems to be over-estimated. However, it is clear from
Figure 8 that preconditioning in the Mach managed to lift
the recovery-mass pull relationships when compared to the
baseline. Based on these results, at the 14 minute reference,
a 4E recovery improvement of 6.0% and 9.5% respectively
after 10 and 15 passes were achieved, at reduced mass pulls
of 8.9% and 5.7% respectively. As is to be expected, this
resulted in increased grades when compared to the baseline,
the 3.1 upgrade ratio of the latter being increased to 3.5
after 10 passes but dropped to below 3 when conditioned
for another 5 passes.
CONCLUSIONS
A set of bench flotation testwork involving the GoldOre
Mach Reactor for high-shear hydrodynamic cavitation
preconditioning of flotation feed was carried out on four
streams of various parts of a SMC concentrator plant pro-
cessing PGM ore. Here, collection of 50 L of hot slurry
samples from the concentrator was followed by passing
the respective samples through the Mach Reactor for dif-
ferent periods of preconditioning. After conditioning with
reagents, the samples were floated in a bench cell for 30
minutes. Interpretation of the results was done by apply-
ing a 2.5 scale-down factor for example, a bench Rougher
feed flotation residence time of 6 minutes was used as refer-
ence for the equivalent plant rougher residence time of 15
minutes.
Preconditioning of the Rougher feed sample with the
Mach Reactor for 5 passes yielded an average 4E recovery
improvement of 8.8% over the baseline (i.e., 0 pass), these
results after 6 minutes of rougher flotation corresponding
to the 15 minutes in the plant. Here, the resultant mass
pulls were similar or slightly higher than that of the base-
line, the higher concentrate grades being attributable to
higher calculated feed grades for the Mach tests (a result of
the fluctuations that are typically experienced when sam-
pling streams on a concentrator at different times). For
the Rougher Scavenger feed stream after 10 minutes (the
equivalent of ~26 minutes in the plant), a 5-pass precondi-
tioning with the Mach returned a slight recovery increase
of 1.3%, increasing to 2.6% after 15 passes, but at the
expense of a higher mass pull. Again, the increased kinetics
after preconditioning all but disappeared towards the latter
stages of flotation.
The Cleaner feed responded well to precondition-
ing, an average 4E recovery improvement of 5.8% being
attained over the baseline at 10 passes, and a 14 minute
residence time (the equivalent of 36 minutes in the plant).
Despite the higher feed grades for the cleaner tests with
the Mach Reactor – an average of around 7.5 g/t vs the
6.9 g/t of the baseline – the upgrade ratios were improved
throughout due to the reduced mass pulls and greater selec-
tivity. The baseline figure of 2.2 was improved to 2.8 after
10 passes, and 2.91 and 2.8 after 20 and 30 passes respec-
tively. Finally, preconditioning in the Mach also managed
to lift the recovery-mass pull relationships for the Final
Tailings when compared to the baseline. At the 14 minute
reference, 4E recovery improvements of 6.0% and 9.5%
respectively was achieved after 10 and 15 passes, accompa-
nied by increased grades due to the reduced mass pulls. The
3.1 upgrade ratio of the baseline was increased to 3.5 after
10 passes.
The mechanism(s) responsible for the peak that is usu-
ally observed in the improvement of kinetics with succes-
sive passes of the feed slurry through the Mach Reactor is
being further researched. Based on our current understand-
ing this can most likely be ascribed to the generation of
slimes that start to negate the effect of nanobubble nucle-
ation, or the increased slurry temperature that could impact
on reagent integrity or activity. This appears to be a func-
tion of several variables, including the type of ore and grade
of the particular feed.
A cost benefit analysis was conducted by plant per-
sonnel assuming a very conservative 2% overall recovery
improvement for the plant and taking into account the
capital costs of purchasing the appropriately sized Mach
Reactors, pumps, tanks, agitators and supports as well as
the operating costs such as power and pump maintenance.
The Mach Reactors themselves require zero maintenance
and have a reactor life to match that of the project. Positive
IRR and impressive NPV numbers were obtained with pay-
back of all of the project capital costs projected at under 6
months.
Tailings sample. As mentioned earlier, for comparative
purposes, an arbitrary retention time of 14 minutes was
chosen for the bench flotation reference, assuming a tail-
ings retreatment plant (TRP) with a capacity of around 36
minutes.
As was the case for the Cleaner feed, interpretation of
the results should be done against the seeming fact that the
assay of the final concentrate in the baseline test (0 pass)
was erroneously over-reported, coupled with an excessive
mass pull. This is also evident from the shape of the other
three curves, as would be expected from a typical bench
float. Likewise, the assay of the first concentrate after 5
passes seems to be over-estimated. However, it is clear from
Figure 8 that preconditioning in the Mach managed to lift
the recovery-mass pull relationships when compared to the
baseline. Based on these results, at the 14 minute reference,
a 4E recovery improvement of 6.0% and 9.5% respectively
after 10 and 15 passes were achieved, at reduced mass pulls
of 8.9% and 5.7% respectively. As is to be expected, this
resulted in increased grades when compared to the baseline,
the 3.1 upgrade ratio of the latter being increased to 3.5
after 10 passes but dropped to below 3 when conditioned
for another 5 passes.
CONCLUSIONS
A set of bench flotation testwork involving the GoldOre
Mach Reactor for high-shear hydrodynamic cavitation
preconditioning of flotation feed was carried out on four
streams of various parts of a SMC concentrator plant pro-
cessing PGM ore. Here, collection of 50 L of hot slurry
samples from the concentrator was followed by passing
the respective samples through the Mach Reactor for dif-
ferent periods of preconditioning. After conditioning with
reagents, the samples were floated in a bench cell for 30
minutes. Interpretation of the results was done by apply-
ing a 2.5 scale-down factor for example, a bench Rougher
feed flotation residence time of 6 minutes was used as refer-
ence for the equivalent plant rougher residence time of 15
minutes.
Preconditioning of the Rougher feed sample with the
Mach Reactor for 5 passes yielded an average 4E recovery
improvement of 8.8% over the baseline (i.e., 0 pass), these
results after 6 minutes of rougher flotation corresponding
to the 15 minutes in the plant. Here, the resultant mass
pulls were similar or slightly higher than that of the base-
line, the higher concentrate grades being attributable to
higher calculated feed grades for the Mach tests (a result of
the fluctuations that are typically experienced when sam-
pling streams on a concentrator at different times). For
the Rougher Scavenger feed stream after 10 minutes (the
equivalent of ~26 minutes in the plant), a 5-pass precondi-
tioning with the Mach returned a slight recovery increase
of 1.3%, increasing to 2.6% after 15 passes, but at the
expense of a higher mass pull. Again, the increased kinetics
after preconditioning all but disappeared towards the latter
stages of flotation.
The Cleaner feed responded well to precondition-
ing, an average 4E recovery improvement of 5.8% being
attained over the baseline at 10 passes, and a 14 minute
residence time (the equivalent of 36 minutes in the plant).
Despite the higher feed grades for the cleaner tests with
the Mach Reactor – an average of around 7.5 g/t vs the
6.9 g/t of the baseline – the upgrade ratios were improved
throughout due to the reduced mass pulls and greater selec-
tivity. The baseline figure of 2.2 was improved to 2.8 after
10 passes, and 2.91 and 2.8 after 20 and 30 passes respec-
tively. Finally, preconditioning in the Mach also managed
to lift the recovery-mass pull relationships for the Final
Tailings when compared to the baseline. At the 14 minute
reference, 4E recovery improvements of 6.0% and 9.5%
respectively was achieved after 10 and 15 passes, accompa-
nied by increased grades due to the reduced mass pulls. The
3.1 upgrade ratio of the baseline was increased to 3.5 after
10 passes.
The mechanism(s) responsible for the peak that is usu-
ally observed in the improvement of kinetics with succes-
sive passes of the feed slurry through the Mach Reactor is
being further researched. Based on our current understand-
ing this can most likely be ascribed to the generation of
slimes that start to negate the effect of nanobubble nucle-
ation, or the increased slurry temperature that could impact
on reagent integrity or activity. This appears to be a func-
tion of several variables, including the type of ore and grade
of the particular feed.
A cost benefit analysis was conducted by plant per-
sonnel assuming a very conservative 2% overall recovery
improvement for the plant and taking into account the
capital costs of purchasing the appropriately sized Mach
Reactors, pumps, tanks, agitators and supports as well as
the operating costs such as power and pump maintenance.
The Mach Reactors themselves require zero maintenance
and have a reactor life to match that of the project. Positive
IRR and impressive NPV numbers were obtained with pay-
back of all of the project capital costs projected at under 6
months.